The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Understanding of the propagation of ultrasound through a bubbly medium is a challenging task because of the nonlinear dynamics of the bubbles and their effect on the attenuation and sound speed of the medium. The majority of the studies on this subject apply linear models, which will generate inaccurate results, especially at higher-pressure excitations. These studies have also ignored the effect...
The drilling process is generally costly and time consuming and prone to serious hazards. Cost-efficiency and enhanced safety measures are vital for any drilling operation. Recent studies indicate that poor reliability in the drilling process resulted in as much as 30% loss of production time. Improved sensor technology with process automation can improve process performance and safety. During drilling...
In cortical bone, osteoporosis impacts both pore size and porosity. A theoretical model predicting ultrasonic parameters based on cortical micro-architectural parameters remains to be developed, and the independent effect of pore size and porosity on ultrasonic parameters remains unclear. Here, we propose a model predicting the attenuation, phase velocity and scattering mean free path (SMFP) in cortical...
Phantoms are objects manufactured using a tissue mimicking material (TMM) and largely used to test protocols and mimic clinical environment for medical training. The TMM should reproduce at least one biological property to allow the association with clinical situation. The gel made by the copolymer styrene-ethylene/butylene-styrene (SEBS) in mineral oil previously reported by our group is a stable...
In vivo estimation of attenuation coefficients is useful because of its potential for tissue characterization and relevance in accurate backscatter coefficient estimation. However, current methods based on spectral analysis for ultrasonic attenuation estimation suffer from a severe trade-off between estimation precision and spatial resolution. Recently, the regularized spectral log difference (RSLD)...
Focused ultrasound (FUS) combined with microbubbles (MBs) has been shown to locally and temporarily open the blood-brain barrier (BBB). However, concurrent opening BBB (long pulse) and mapping the location of BBB opening (short pulse) by pulsed-wave excitation always conflicts. Previously proposed passive cavitation imaging in brain suffered from degraded axial resolution because of long driving pulse...
Functional Ultrasound (fUS) has shown to be a promising new neuroimaging modality that uses ultrafast plane waves to detect changes in cerebral blood flow for imaging brain activity at high spatiotemporal resolution. An existing challenge is the ultrasound penetration of skull which decreases with frequency. In the initial study (Macé et al., 2011)[1] a craniotomy was required to perform fUS. Since...
Sulphate attack is considered one of the most aggressive causes of concrete degradation. Ettringite triggers expansion mechanisms that have harmful effects on the Portland cement matrix, causing micro-cracking and, consequently, a reduction in the stiffness and strength of concrete. Portland cement composites are very dispersive and heterogeneous materials that makes very challenging to do non-invasive...
The technique of non-invasive cortical bone quality assessment using ultrasound axial transmission has attracted considerable attention. Estimating the phase velocity and the attenuation of the absorbing plate will assist the assessment. Among several techniques proposed for these purposes, many employ either a thresholding process or a peak search process. The thresholding process uses the intensity...
Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease and can often lead to fibrosis, cirrhosis, cancer and complete liver failure. Liver biopsy is the current standard of care to quantify hepatic steatosis but it comes with increased patient risk and only samples a small portion of the liver. Imaging approaches to assess NAFLD include proton density fat fraction...
One of the major cause for the attenuation of ultrasonic waves in polycrystalline materials is the random scattering at the grain boundaries — grain boundary scattering (GBS) —, whereby the acoustic mismatch is the result of the random orientation of the mechanical properties of the single crystals within the individual grains. Various analytical models, such as the unified theory, have been developed...
Diagnosis and assessment of liver fibrosis grade required for management is mainly based on blood tests and invasive hepatic puncture-biopsy. Quantitative UltraSound (QUS) techniques provide insight into tissue microstructure and are based on the frequency-based analysis of the signals from biological tissues. This study aims to explore the diagnostic performance of QUS technique in high frequency...
Leaky surface acoustic waves (LSAWs) and longitudinal-type LSAWs (LLSAWs) have a number of beneficial characteristics such as a larger electromechanical coupling factor K2 and higher phase velocity than those of Rayleigh-type SAWs. However, LSAWs and LLSAWs have inherent attenuation because they lose energy by continuously radiating bulk waves into the substrate. To solve this problem, the authors...
Ultrasound shear wave elastography is a well established tool for characterization of biologic tissues. While it has found applications in various medical disciplines such as oncology and urology its feasibility for pneumology still has to be shown. We provide experimental results of ultrasound shear wave elastography of soft porous materials in phantoms. Shear wave dispersion and evidence of the...
Recently, it has been developed a sound source capable of irradiating aerial ultrasonic waves of very high intensity, and researches on applied technologies utilizing the ultrasonic power have been actively conducted. In these applied technologies, it is necessary to irradiate sound waves to the object under optimum conditions. However, this technique has a problem that optimum sound wave irradiation...
Optical ultrasound sources, which generate ultrasound photoacoustically, are promising alternatives to piezoelectric or capacitive transducers. Employing pulsed excitation light, high bandwidths (up to 100 MHz) and pressures (MPa range for unfocussed sources) have been achieved with materials that combine strong optical absorption with a high thermal expansion coefficient, such as carbon nanotube...
Shear wave (SW) propagation in viscoelastic materials is characterized by a complex, frequency-dependent shear modulus μ(f). Measurements of μ(f) typically require Fourier transform techniques to decompose an observed SW signal into discrete frequency components and two independent measurements such as the phase velocity c(f) and attenuation α(f) to determine the real and imaginary parts of μ(f).
Transcranial focused ultrasound is being researched as a noninvasive means of ablating brain tumors and of increasing delivery of cancer therapeutics through the blood-brain barrier. However, the current techniques are implemented by means of a large-aperture spherical transducer. The geometric focus of these transducers limits the treatment envelope to the center of the brain, whereas the majority...
Future China mission to explore the planet Mars may carry acoustic probes. Because sound interacts with matter intimately, they could be used in Mars to measure the wind speed directly, to record the possible ambient sounds, and to assist the safety of a travelling Lander by inspecting obstacles and by detecting a soft subsurface soil which might cause the Lander being trapped. All these Martian acoustic...
Porous piezoelectric ceramics are often integrated as constitutive elements in several devices such as ultrasound transducers. For high-frequency (HF) applications (i.e., >20 MHz), unpoled, porous lead zirconate titanate (PZT) can be used as a backing. The porosity content allows the acoustical impedance value to be adjusted but it also affects the acoustic attenuation according to the size and...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.